Variable angle locking implant

ABSTRACT

A variable angle locking implant includes a bone plate having a lower surface, an upper surface, and at least one opening extending from the lower surface to the upper surface along an axis. The opening has a plurality of fins oriented along a plane. The axis is non-perpendicular to a tangent of a projection of the lower surface across the opening, the tangent defined at the intersection between the axis and the projected lower surface, and/or the plane is non-parallel to the tangent. The implant includes at least one fastener, and the plurality of fins are deflectable relative to a head portion of the fastener such that the fastener can be inserted and retained at any one of a plurality of angles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of co-pending U.S. patentapplication Ser. No. 13/524,506, filed Jun. 15, 2012, entitled “VariableAngle Locking Implant”, which application claims priority to and thefull benefit of U.S. Provisional Application Ser. No. 61/497,180 filedJun. 15, 2011, and titled “Variable Angle Locking Implant,” the entirecontents of which are incorporated herein by reference.

TECHNICAL FIELD

This invention relates to a variable angle locking implant.

BACKGROUND

Variable angle locking implants for repairing bone fractures have beendescribed, for example, in U.S. patent application Ser. No. 12/484,527,filed Jun. 15, 2009, published as U.S. Publication No. 2009/0312803,hereby incorporated herein by reference in its entirety. In particular,U.S. Publication No. 2009/0312803 describes an implant having fastenerreceiving holes with fins that permit a fastener to be positionedoff-axis within the hole.

Implants such as bone plates have been provided with threaded holes(that may receive either locking screws or non-locking screws),non-threaded holes (for non-locking screws), partially threaded slots toallow either non-locking or locking screws to be used together, andcombinations of the above.

SUMMARY

The variable angle locking implant provides a stable connection betweena bone and a bone plate using a fastener that permits different anglesto be obtained between the bone plate and the fastener, while thefastener also locks into the bone plate. This allows the surgeon toreach denser areas of bone or capture random bone fragments that are inirregular positions, for example, in cases of severe fractures withhighly fragmented bones. The fastener and plate system advantageouslyallows the surgeon to choose the angle at which the screw is insertedthrough, and rigidly affixed in, an opening of the plate.

The variable angle locking implant allows a surgeon to direct thefastener toward bone fragments that are not necessarily located alongthe axis of the opening in the plate. It also provides flexibility inthe placement of the plate in relation to the bone fracture. Allowingsurgeons to choose the angle at which the fastener is inserted into theplate leads to better tailoring of the system to the specific nature ofthe bone fracture to be treated, and allows surgeons to adjust theirstrategy as necessary after the surgical site has been accessed, butprior to insertion of the fastener into bone material.

According to one aspect, a variable angle locking implant includes abone plate having a lower surface, an upper surface, and at least oneopening extending from the lower surface to the upper surface along anaxis. The opening has an inner surface with a plurality of fins orientedalong a plane. The axis is non-perpendicular to a tangent of aprojection of the lower surface across the opening, the tangent definedat the intersection between the axis and the projected lower surface,and/or the plane is non-parallel to the tangent.

Implementations of this aspect may include one or more of the followingfeatures.

For example, the lower surface includes a bone conforming arcuatesurface. The lower surface is adapted to contact a distal femur, aproximal femur, a distal tibia, a proximal tibia, a proximal humerus, adistal humerus, a clavicle, a fibula, an ulna, a radius, a distalradius, a rib, pelvis, a vertebra, bones of the foot, or bones of thehand, shaft fractures on long bones, or any of the aforementionedadjacent bones in the case of a joint fusion plate.

The fins are positioned within the opening. The axis is perpendicular tothe tangent and the plane is non-parallel to the tangent. Alternatively,the axis is non-perpendicular to the tangent and the plane isnon-parallel to the tangent, for example, the plane is perpendicular tothe axis.

The fins are integrally connected to, and protruding from, the innersurface. The opening has a radius between the inner surface and the topof the fins, and each fin tapers in thickness from the inner surfacetowards its terminal end. The opening has a jagged circumference formedby protruding fins at the lower surface. The protruding fins form aconcave portion of the inner surface. The protruding fins have basesthat meet the inner surface along the plane. The fins have a taperedshape or a straight shape. The fins are provided in more than one layer.The fins are trapezoidally-shaped, rounded, oval, rectangular, curved,rhomboid, diamond-shaped, or triangular. The edges of the fins taperinwardly, outwardly, or are about parallel with one another. There areat least 3, but no more than 10, fins integrally connected to, andprotruding from, the inner surface. The fins are provided as a series ofconcavely indented, inwardly protruding fins that are adapted to securea threaded head of a fastener in place at varying angles.

The bone plate includes one or more of the following openings: athreaded opening; a non-threaded opening; an opening adapted to receivelocking or non-locking fasteners; an opening with fins; a provisionalfixation opening; a combination slot; or any combination thereof.

The implant includes at least one fastener. The fastener is at leastpartially threaded and has a head portion and a shaft portion. Theopening is adapted to receive the fastener without being tapped by thefastener. The plurality of fins are deflectable relative to the headportion of the fastener when the fastener is inserted into the openingsuch that the fastener can be inserted and retained at any one of aplurality of angles relative to the opening. The fins are deflectable sothat the fins are interposed between the threads of the fastener. Theinner surface includes threads located above or below the fins.

According to another aspect, a method for securing a bone plate to abone includes placing a lower surface of the bone plate against thebone; inserting a fastener into an opening in the bone plate, theopening having an axis that is non-perpendicular to a tangent of aprojection of the lower surface across the opening, the tangent definedat the intersection between the axis and the projected lower surface;selecting a trajectory of the fastener into the bone, the trajectorybeing up to about 15 degrees off the hole axis; and inserting thefastener into the bone.

Implementations of this aspect may include one or more of the followingfeatures.

For example, either a locking screw or a non-locking screw is insertedin the opening. The fastener is removed and re-inserted into the openingof the bone plate at any one of a plurality of angles. Inserting thefastener into the bone includes drawing a bone fragment into alignmentwith an intact bone segment.

The details of one or more implementations of the invention are setforth in the accompanying drawings and the description below. Otherfeatures, objects, and advantages of the invention will be apparent fromthe description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a variable angle locking implant positionedon a bone.

FIG. 2 is a cross-sectional view of the variable angle locking implanttaken along line 2-2 of FIG. 1.

FIG. 3 is a perspective view of a bone plate and fastener of thevariable angle locking implant.

FIG. 4 is a perspective view of a bone plate of the variable anglelocking implant having a finned opening.

FIGS. 5A-5E are cross-sectional views of various implementations of thefinned opening.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, a variable angle locking implant 2 forrepairing fractures in bone 4 includes a bone plate 40 and one or morefasteners 90. A fastener 90 is shown engaged in a finned opening 50 thatextends between an upper surface 44 and a lower, bone contacting surface42 of the bone plate 40. The fastener 90 can be positioned in theopening 50 and fixed in the plate 40 at various insertion angles tocapture “renegade” or random bone fragments that have split from thebone during fracture and secure the bone fragments to the plate 40.

The fastener 90 shows a new trajectory achieved by increasing the rangeof angles as compared to the screw 90 a. For example, the central axis96 of fastener 90 has an approximate 15 degree offset from the centralaxis 52 and approximately 30 degree offset from perpendicular to thelower surface 42 of the bone plate 40. The alternative placement of ascrew 90 a in a hole having an axis 52 perpendicular to the lowersurface 42 of the plate 40 and a plane 59 that is parallel to the bottomlower surface 42 illustrates approximately a 15 degree offset from thecentral axis 52 and a corresponding approximately 15 degree offset fromperpendicular to the lower surface 42 of the bone plate 40, thusillustrating the greater range of the insertion angle of the fastener90.

The locking implant 2 also includes a provisional pin opening 102 aswell as a combination slot 104.

Referring also to FIGS. 3 and 4, the plate 40 has an inner surface 54that defines the opening 50 and a series of concavely indented, inwardlyprotruding fins 56 that extend toward a central axis 52 of the opening50. Each fin 56 has a base 58 and the bases 58 form concave portions 60.The bases 58 of the fins 56 all meet, for example, in substantially thesame plane 59 a-59 d (FIGS. 5A-5D) and then angle downwardly andinwardly at a similar angle or slope. As discussed further below, thecentral axis 52 can be oriented non-perpendicular to the lower surface42 and/or the planes 59 a-59 d can be oriented non-parallel to the lowersurface 42 to increase the range of possible insertion angles.

The concave portions 60 are smooth and non-threaded, and as illustrated,the entire inner surface 54 of the finned opening 50 can be devoid ofthreads. The lack of threads helps ease the manufacturing of the plate40, and allows the plate 40 to be manufactured as thinly as desired. Thebases 58 can extend from the inner surface 54 at or near an uppercircumference 62 of the inner surface, at a middle region of the innersurface, or at or near a lower circumference of the inner surface. Withthe fins 56 located adjacent a lower circumference at the lower, bonecontacting surface 42 of plate 40, the lower circumference appearsjagged due to the presence of the fins, while the upper circumference 62is smooth.

As the fins 56 extend toward central axis 52, they taper to form taperedsides 64. The fins 56 end at rounded tips 66, although tips 66 can bepointed, square, rectangular, or any other appropriate configuration.For example, as described in U.S. Patent Application Publication No.2009/0312803, which is incorporated herein by reference in its entirety,the fins 56 can have straight edges or sides and straight ends such thatthe fins are partially rectangular-shaped with slit-shaped openingsbetween the fins. Alternatively, the fins can be more triangular inshape having sides that taper inwardly and end edges that are flat andsmall. Other example fin shapes include trapezoidal, square, round,circular, triangular (with a pointed tip).

The dimensions of fins 56 are typically dependent at least in part uponthe pitch and threads of the fastener 90. For example, a larger plate 40for use with a larger fastener 90 (for example, for use on a femur bone)will likely be thicker and will have larger and thicker fins 56 than asmaller plate 40 (for example, for use on a smaller bone). In specificimplementations, the fins 56 are particularly thin so that they can bemoved up or down and deformed under pressure. In some implementations,the fins 56 may be pressed toward the edges of the finned opening 50. Anon-limiting exemplary range of thicknesses for the fins 56 is fromabout 0.15 mm to about 5 mm, although larger and smaller sizes arepossible. The fins 56 are intended to fit between threads 98 on thethread form of fastener 90, as shown in FIG. 3.

Providing a non-threaded inner surface 54 also allows the fastener 90 tobe inserted into the finned opening 50 at any desired insertion angle,that is the angle defined between a longitudinal axis 96 (FIG. 2) of thefastener 90 and the central axis 52 (FIG. 4) of the finned opening 50.The central axis 52 and the longitudinal axis 96 can be co-linear sothat the insertion angle is zero, or the central axis 52 and thelongitudinal axis 96 (FIG. 1) can be non-co-linear with an insertionangle of up to about +/−15 degrees. Varying the insertion angle ispossible because there are not any threads in the finned opening 50 tointerfere with the desired insertion angle. The fins 56 are intended toslightly bend or deform in order to secure the fastener 90 in place inthe finned opening 50. The fins 56 engage the threads 98 or othersurface of the fastener 90.

The fastener 90 has a head 94 and a shaft 92. The shaft 92 may bethreaded or non-threaded. The head 94 of the fastener 90 has at leastone set of threads 98 and a bore 18 for receiving a driver in order todrive the fastener 90 through the plate 40 and into bone. The threads 98are typically any standard-type thread.

Referring to FIGS. 5A and 5B, the central axis 52 a, 52 b of the opening50 can be oriented non-perpendicular to the lower surface 42 of theplate 40, for example, at an angle, θ, in the range between 0 and 90degrees. In FIG. 5A, two rows of fins 56 are illustrated that each liein a plane 59 a that is parallel to the lower surface 42 of the plate40. In FIG. 5B, the fins 56 lie in a plane 59 b that is orientednon-parallel to the lower surface 42 of the plate 40, for example, theplane 59 b is perpendicular or nearly perpendicular to the axis 52 b. InFIG. 5C, the fins 56 are illustrated lying in a plane 59 c that isoriented non-parallel to the lower surface 42 of the plate 40 and theplane 59 c is non-perpendicular to the axis 52 c. The fins 56 of FIGS.5B and 5C are positioned within the opening 50, that is, between theupper surface 44 and lower surface 42 of the plate 40.

The non-perpendicular orientation of the central axis 52 a, 52 b, 52 dand/or the non-parallel orientation of the plane 59 b-d increases theuseful range of possible insertion angles as compared to a bone plate 40having the central axis 52 perpendicular to the lower surface 42 and theplane 59 parallel to the lower surface 42. For example, referring toFIG. 5B, assuming θ is 15 degrees, a fastener 90 could be inserted withthe fastener axis 96 aligned with axis 52 b, and thus 15 degrees offfrom perpendicular to the lower surface 42, or the fastener axis 96could be tilted up to, for example, +/−15 degrees, such that thefastener axis 96 is perpendicular to the lower surface 42 or up to 30degrees off from perpendicular to reach bone fragments. Increasing therange of angles allows the surgeon to target new fastener trajectoriesin the bone as shown in FIG. 2.

The screw 90 (FIG. 2) shows a new trajectory achieved by increasing therange of angles as compared to the screw 90 a. The fastener 90 is shownpositioned in the hole of FIG. 5B and having a 15 degree offset from thecentral axis 52 and 30 degree offset from perpendicular to the lowersurface 42 of the bone plate 40. The alternative placement of a screw 90a in a hole having an axis 52 perpendicular to the lower surface 42 ofthe plate 40 and a plane 59 that is parallel to the lower surface 42illustrates a 15 degree offset from the central axis 52 and only acorresponding 15 degree offset from perpendicular to the lower surface42 of the bone plate 40, thus illustrating the greater range of theinsertion angle of the fastener 90. Angling the screw greater than 15degrees from the central axis 52 of an opening having an axis 52perpendicular to the lower surface 42 of the plate 40 and a plane 59that is parallel to the lower surface 42 produces inconsistent failureloads. Therefore, to achieve a screw trajectory greater than 15 degreesfrom the lower surface 42 of the plate 40 while maintaining the abilityto capture and secure bone fragments, the angle of the central axis 52is offset from perpendicular to the lower surface 42 and the screw axis96 tilted to reach a maximum of 30 degrees offset.

Referring to FIG. 5D, the range of insertion angles can also beincreased by orienting the axis 52 d of the opening 50 perpendicular tothe lower surface 42 of the plate 40, while the fins 56 lie in a plane59 d that is non-parallel to the lower surface, for example, at anangle, α, in the range between 0 and 90 degrees.

The finned opening 50 can include about five to eight fins 56, asillustrated, two or three fins 56, or ten or twenty or more fins 56,depending upon the plate 40 for which the finned opening 50 is intendedfor use. The finned holes can optionally include threads 112 (FIG. 5B)formed above or below the fins in the inner surface of the hole. Theregion of the opening above the fins can taper inwardly from the uppersurface of the plate, for example, at an angle of about 5 to 15 degrees,and the region of the opening below the fins can taper outwardly towardthe lower surface of the plate, for example, at an angle of about 40 to50 degrees. The finned opening 50 can optionally be a slot hole orcombination hole with half or more of the length of the opening can befinned with the remainder of the opening being non-threaded for slidingcompression.

The primary purpose of fins 56 is to grasp one or more threads 98 of thefastener 90 in order to secure the fastener 90 in place in the boneplate 40 at any desired insertion angle. Fasteners 90 received indifferent finned openings 50 can be inserted at the same or differentinsertion angles. As a fastener 90 is inserted, its threads 98 start toengage the fins 56, as shown in FIG. 3. As discussed above, the fins 56can be very thin so that as the threads 98 start to grab the fins 56,the fins 56 can move up or down as appropriate to engage the threads 98and secure the fastener 90 in the finned opening 50. The threads 98engage the fins 56 so that the fins 56 fit between the threads 98. Themovement of fins 56 can be a permanent deformation, so that the fins 56cannot flex back and allow the fastener 90 to work its way out.

The finned openings 50 can be provided on all types of bone plates 40and can be combined with other types of openings. As illustrated in FIG.1, there can be finned openings 50, a threaded opening 30, and aprovisional pin opening 102. Other options are holes that can be usedwith either a threaded or non-threaded fastener, as well as combinationslots 104. For example, a slot having fins mounted on either or bothends of the slot for static locking and no threads or fins in the middleportion of the slot for dynamic locking These various types of openingsmay be used on any type of bone plate, in any combination and in anysize. The inclusion of a plurality of finned openings 50 in the boneplate 40 can help achieve better fixation of a fractured bone, forexample, where numerous fragments have shattered in various directions,because the fasteners 90 can be inserted at various angles to capture“renegade” or random bone fragments that have split from the bone duringfracture, but still secure the bone fragments to the plate 40.

The threads 98 on fastener 90 can be any type of standard ornon-standard thread. For example, the threads 98 can be a continuousridge or a non-continuous ridge. The threads 98 can form a portion of arevolution, one complete revolution, multiple revolutions, a singlelead, or multiple leads, or any other threads known in the art.Additionally or alternatively, the head 94 of fastener 90 can includeany other surface that will engage with and seat within the fins 56 ofthe finned opening 50. For example, the head 94 can have a series ofdimples, ridges, bumps, textured areas, or any other surface that cansecure fastener 90.

The fastener 90 may be any typical fastener, made out of any appropriatematerial. The fastener 90 typically has a bore 18 for receiving a driverin order to drive the fastener 90 through the plate 40 and into bone.The bore 18 may be any size and shape, for example, it may have ahexagonal configuration to receive a corresponding hexagonal driver, aPhillips screw head, a flat-head, a star configuration, Torx, or anyother appropriate configuration that can cooperate with a driver todrive the fastener 90 into the plate 40.

The shaft 92 may be fully threaded, partially threaded, or a helicalblade, and/or may include one or more tacks, deployable talons,expandable elements, or any feature that allows shaft 92 to engage bone.It is also possible that shaft 92 is not threaded, so that fastener 90takes the form of a peg or a pin. This alternative implementation may bepreferred in certain procedures where, for instance, the main goal is toprevent tilting of a bone segment or in procedures where there is noconcern of fastener 90 pulling out from the bone and hence no need forshaft 92 to be threaded or otherwise configured to engage bone. The endof shaft 92 may be a self-tapping or self-drilling tip.

The bone plate 40 may be adapted to contact one or more of a distalfemur, a proximal femur, a distal tibia, a proximal tibia, a proximalhumerus, a distal humerus, a clavicle, a fibula, an ulna, a radius, adistal radius, a rib, pelvis, a vertebra, bones of the foot, or bones ofthe hand, shaft fractures on long bones, or any of the aforementionedadjacent bones in the case of a joint fusion plate. The bone plate 40may be curved, contoured, straight, or flat. The lower, bone contactingsurface 42 can have an arcuate shape that conforms to the bone. Forexample, referring to FIG. 5E, the bone plate 40 is shown with a bonecontacting surface 42 having an arcuate or curved shape. In theimplementation shown, the central axis 52 of the opening 50 can beoriented non-perpendicular to a tangent line or tangent plane T-T of theprojected arcuate bone contacting surface 42 that intersects the centralaxis 52 at a point P along the projected bone contacting surface 42, forexample, at an angle, θ, in the range of between 0 and 90 degrees. InFIG. 5E, a row of fins 56 is illustrated that each lie in a plane 59 ethat is oriented non-parallel to the tangent line or plane T-T. The fins56 can alternatively be located at the lower surface 42 and also have anarcuate shape that conforms to the bone. The plate can be aperiarticular plate or a straight plate. The plate may have a headportion that is contoured to conform to a particular bone surface, suchas a metaphysis or diaphysis, that flares out from the shaft portion,that forms an L-shape, T-shape, Y-shape, with the shaft portion, or thatforms any other appropriate shape to fit the bone to be treated.

The bone plate 40 can be made from metal, a resorbable or non-resorbableplastic, ceramic, or composite materials. Suitable materials mayinclude, for example, titanium, stainless steel, cobalt chrome,polyetheretherketone (PEEK), polyethylene, ultra high molecular weightpolyethylene (UHMWPE), resorbable polylactic acid (PLA), polyglycolicacid (PGA), combinations or alloys of such materials or any otherappropriate material that has sufficient strength to be secured to andhold bone, while also having sufficient biocompatibility to be implantedinto a body.

Turning now to the methods of implantation, the surgeon accesses thesurgical site of interest, which can be an internal site at which a bonefracture is located that requires stabilization to ensure properhealing. The fracture may be reduced with conventional forceps andguides (which are known to those in the art), and a bone plate 40 ofappropriate size and shape is placed over the fracture site. In someinstances, the bone plate 40 may be temporarily secured to the bone 4using provisional fixation pins. The provisional fixation pins may beused through either the provisional pin openings 102, or any otheropening in the plate 40. Provisional fixation provides for temporarilysecuring the bone plate 40 to the bone 4 before placing fixation screwsthrough the bone plate 40, so that one can be certain the bone plate 40is properly positioned before placing bone screws for permanent fixationof the bone plate 40 to the bone 4. Moreover, with provisional fixation,x-rays can be taken of the bone plate/construct without excessinstruments in the field of view.

Once the plate 40 is secured at a desired location in relation to thefracture (typically using one or more provisional fixation pins,although any other appropriate method may be used), the surgeon thenidentifies an insertion angle at which the fastener 90 is to be insertedthrough a selected opening 50 and driven into bone material 4. If thebone plate 40 includes more than one opening 50, the surgeon alsoselects the specific opening 50 to be used. After selecting the desiredinsertion angle and the opening 50, the surgeon inserts the shaft 92 ofthe fastener 90 through the opening 50 until the tip contacts bonematerial 4. In some cases, a hole may need to be drilled or tapped intothe bone 4 along the insertion angle to facilitate the initial tappingor insertion of the fastener 90. The surgeon then uses an appropriatedriving tool in the bore 18 of the head 94 to manipulate the fastener 90into place.

Because the fastener 90 can be inserted at angles up to about 60 degreesfrom perpendicular to the lower surface of the plate, the fastener 90can be used to grab and/or secure bone fragments that are out of linewith the traditional angle at which a locking screw would normally beinserted. The surgeon may need to toggle or maneuver the fastener 90 inorder to secure and draw in displaced bone fragments.

Once the bone fragment is secured, the fastener 90 is ready to besecured to the plate 40. As the fastener 90 is driven further into bone4, it is also drawn further into the plate 40. As the threads 98 of thefastener head 94 begin to contact the fins 56, the fins 56 engage withinthe threads 98 to hold the fastener 90 in place at the desired insertionangle. The action of engagement between the fins 56 and the threads 98rigidly affixes the fastener 90 to the bone plate 40 at the desiredinsertion angle.

The surgeon may then use traditional locking and/or non-locking screwsin other openings on the plate 40. This can help further secure the boneplate 40 to the bone fracture if needed.

Once all the fasteners and/or screws are placed, the surgeon may placecovers over the unused openings, particularly if there are any unusedopenings that cross the fracture, to strengthen the plate 40.Additionally or alternatively, the surgeon may use bone graft material,bone cement, bone void filler, and any other material to help heal thebone.

In practice, a first screw is initially inserted through a bone plate 40and into a bone 4 on one side of a fracture and then a second screw isinserted through the bone plate 40 on the opposite side of the fracture.In particular, after the first screw is in place, an axial compressionscrew is inserted through a hole in the bone plate 40 on a side of thefracture opposite the side of the first screw. The compression screw maybe inserted through the hole and into the bone 4 such that as thecompression screw is fully inserted, the bone plate 40 is drawn over toa desired position. By moving the bone plate 40, the tissue is pulledtogether to reduce the fracture. Once the compression screw has beenused to move the bone plate 40 into the desired position, thecompression screw may be removed from the bone 4 and bone plate 40 and alocking screw may be inserted through the opening 50 in the bone plate40 and in the bone 4 in the space formerly occupied by the compressionscrew. The locking screw can then be tightened to lock the plate 40 intoposition. The replacement of the compression screw with the lockingscrew is not required, but a locking screw may provide more stabilityand rigid fixation than leaving the compression screw in place. In somemodes of operation, a locking screw is placed directly in a locking holewithout first inserting a compression screw in the hole.

A number of implementations of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other implementations are within the scope of the followingclaims. For example, locking screws, non-locking screws, or otherfasteners may be used. One or more openings having a non-perpendicularorientation of the central axis 52 and/or the non-parallel orientationof the plane 59 can be employed to receive a fastener in implants otherthan plates, such as in an acetabular cup or glenoid base component, toincrease the useful range of possible insertion angles of the fastener.According to another implementation, the head of the screw 94 caninclude the fins 56 and the opening 50 can be threaded, with the openinghaving a non-perpendicular orientation of its central axis 52 and/or theplane 59 defined by the fins 56 having a non-parallel orientation.

What is claimed is:
 1. An implant comprising: a first surface; a secondsurface; and at least one opening extending from the first surface tothe second surface, the at least one opening having an inner surfaceincluding a first plate member including a plurality of upper fins and asecond plate member including a plurality of lower fins, wherein theplurality of upper fins define an upper, circumferential edge to contacta head of a bone fastener in use and the plurality of lower fins definea lower, circumferential edge to contact the head of the bone fastenerin use, the plurality of upper fins are positioned closer to the firstsurface of the implant and the plurality of lower fins are positionedcloser to the second surface of the implant; and wherein at least one ofthe plurality of upper fins and the plurality of lower fins are adaptedand configured to deform in order to secure a position of the head ofthe bone fastener inserted into the at least one opening; and whereinthe at least one opening has a radius between the inner surface and atop surface of the upper fins, and each fin tapers in thickness from theinner surface towards a terminal end.
 2. The implant of claim 1, whereinthe at least one opening includes an axis, the axis of the at least oneopening is oriented non-perpendicular to the first and second surfacesof the implant.
 3. The implant of claim 1, wherein the plurality ofupper fins and the plurality of lower fins each include five to eightfins.
 4. The implant of claim 1, wherein each of the plurality of upperand lower fins include inwardly tapered side surfaces.
 5. The implant ofclaim 1, wherein the implant is a bone plate.
 6. The implant of claim 1,wherein the implant is an acetabular cup.
 7. The implant of claim 1,wherein at least one of the plurality of upper fins and at least one ofthe plurality of lower fins cooperate with the head of the bonefastener.
 8. The implant of claim 1, wherein each of the plurality ofupper fins and each of the plurality of lower fins cooperate with thehead of the bone fastener.
 9. The implant of claim 1, wherein theplurality of upper fins lie in a first plane and the plurality of lowerfins lie in a second plane, the first plane and the second plane beingparallel relative to each other.
 10. The implant of claim 1, wherein theplurality of upper fins lie in a first plane and the plurality of lowerfins lie in a second plane, the first plane and the second plane beingparallel to the second surface of the bone plate.
 11. The implant ofclaim 1, wherein the plurality of upper fins and the plurality of lowerfins are provided as a series of concavely indented, inwardly protrudingfins.
 12. The implant of claim 1, further comprising at least one bonefastener, the at least one fastener being at least partially threadedand having a head and a shaft, wherein the at least one opening isadapted to receive the at least one bone fastener, and wherein theplurality of upper fins and the plurality of lower fins are deformablerelative to the head of the at least one bone fastener so that when theat least one bone fastener is inserted into the at least one opening,the at least one bone fastener is retained at any one of a plurality ofangles relative to the at least one opening.
 13. The implant of claim 1,wherein the first and second plate members are integrally formed withthe implant.
 14. An implant comprising: a first surface; a secondsurface; and an opening extending from the first surface to the secondsurface, the opening having an inner surface including a first platemember including a plurality of upper fins and a second plate memberincluding a plurality of lower fins, wherein the plurality of upper finsdefine an upper, circumferential surface including a series of concaveand convex surfaces to contact a head of a fastener in use and theplurality of lower fins define a lower, circumferential surfaceincluding a series of concave and convex surfaces to contact the head ofthe fastener in use, the plurality of upper fins are positioned closerto the first surface of the implant and the plurality of lower fins arepositioned closer to the second surface of the implant; and wherein atleast one of the plurality of upper fins and the plurality of lower finsare adapted and configured to deform in order to secure a position ofthe head of the fastener in use; and wherein the opening has a radiusbetween the inner surface and a top surface of the upper fins, and eachfin tapers in thickness from the inner surface towards a terminal end.15. An implant comprising: a first surface; a second surface; and anopening extending from the first surface to the second surface, theopening having an inner surface including an integrally formed firstplate member including a plurality of integrally formed upper fins andan integrally formed second plate member including a plurality ofintegrally formed lower fins, wherein the plurality of upper fins definean upper, circumferential surface including a series of concave andconvex surfaces to contact a head of a fastener in use and the pluralityof lower fins define a lower, circumferential surface including a seriesof concave and convex surfaces to contact the head of the fastener inuse, the plurality of upper fins are positioned closer to the firstsurface of the implant and the plurality of lower fins are positionedcloser to the second surface of the implant; and wherein at least one ofthe plurality of upper fins and the plurality of lower fins are adaptedand configured to deform in order to secure a position of the head ofthe fastener in use; and wherein the opening has a radius between theinner surface and a top surface of the upper fins, and each fin tapersin thickness from the inner surface towards a terminal end.